A method for compensating the signal-to-noise ratio of intermittent transmission and reception of linear frequency modulated signals in a microwave anechoic chamber RF radiation simulation

Abstract

This invention discloses a method for signal-to-noise ratio (SNR) compensation of intermittent transmission and reception of linear frequency modulated (LFM) signals in microwave anechoic chamber radio frequency radiation simulation. The method involves three steps: first, calculating the peak power loss of the LFM signal after intermittent transmission and reception; second, calculating the average power loss after intermittent transmission and reception; and third, performing SNR compensation through energy modulation of the transmitted signal. This method utilizes the relationship between the SNR of the complete signal after intermittent transmission and reception processing and the SNR of the signal after intermittent processing to compensate for the input signal power, providing a convenient and efficient way to obtain the SNR of the LFM signal after intermittent transmission and reception in a microwave anechoic chamber. This method effectively solves the signal-to-noise ratio loss caused by intermittent transmission and reception processing, thereby achieving an equivalent simulation of the SNR of the LFM signal in an anechoic chamber and providing theoretical support for the equivalent simulation of radar power in radiation simulation.

Description

[Technical Field]

[0001] This invention relates to a method for compensating the signal-to-noise ratio (SNR) of intermittent transmission and reception of linear frequency modulated (LFM) signals in a microwave anechoic chamber radio frequency radiation simulation, belonging to the field of radar system simulation. Specifically, it involves processing LFM signals in a microwave anechoic chamber using an intermittent transmission and reception method, and then compensating for the energy of the transmitted radar signal to solve the problem of SNR loss caused by intermittent transmission and reception. [Background Technology]

[0002] Because common microwave anechoic chambers are relatively small, they can cause coupling between the transmitted signal and the echo during radio frequency radiation simulation experiments, making it difficult to achieve effective echo acquisition and reception. However, this problem can be effectively solved by intermittently processing the signal transmission and reception.

[0003] Linear frequency modulated (LFM) signals, as a commonly used pulse signal, are characterized by a large time-bandwidth product, allowing for a high compression ratio during pulse compression. Furthermore, the matched filters used in LFM signals are insensitive to Doppler shift in the echo signal, significantly simplifying radar signal processing systems and leading to their widespread application in engineering. However, intermittent transmission and reception processing of LFM signals in a microwave anechoic chamber splits the complete LFM signal into several short pulses, causing discontinuities in the time domain and resulting in signal power loss. Compared to real radar signals, the signal-to-noise ratio (SNR) of the intermittently transmitted signal is reduced, affecting subsequent measurements of key radar performance indicators such as detection capability and causing numerous inconveniences for subsequent processing.

[0004] Therefore, it is necessary to design a suitable method to compensate for the signal-to-noise ratio (SNR) of the linear frequency modulated (LFM) signal after intermittent transmission and reception processing. However, there is currently no relevant method to solve the problem of reduced SNR. This invention will study a method for compensating the SNR of LFM signal transmission and reception in this microwave anechoic chamber RF radiation simulation. [Summary of the Invention]

[0005] The technical problem to be solved by this invention is to design a signal-to-noise ratio compensation method for intermittent transmission and reception of linear frequency modulated signals in microwave anechoic chamber radio frequency radiation simulation, so as to solve the problem of signal-to-noise ratio loss caused by intermittent transmission and reception of linear frequency modulated signals, thereby achieving equivalent signal-to-noise ratio in the anechoic chamber.

[0006] The technical solution adopted is as follows:

[0007] The first step is to calculate the peak power loss after intermittent transmission and reception of the linear frequency modulated signal.

[0008] The intermittently transmitted signal p(t) is a pulse train with a rectangular envelope. After the linear frequency modulated signal x(t) is processed by the intermittently transmitted signal, the pulse will be truncated into a series of sub-pulses x. sBy comparing the intermittently processed signal and the complete signal after they have both been processed by the matched filter H(f), the peak power loss after the matched filter can be obtained.

[0009] The second step is to calculate the average power loss after intermittent transmission and reception in the noise.

[0010] The complete noise n(t) and the noise n after intermittent transmission and reception processing are combined. s After matched filtering, the average output power of each (t) is E. n and E ns By comparing the two, we can obtain the average power loss of the noise after intermittent transmission and reception.

[0011] The third step is to perform signal-to-noise ratio compensation by modulating the transmitted signal energy.

[0012] The signal-to-noise ratio (SNR) of a matched filter output is the ratio of the peak power of the output signal to the average power of the noise. By comparison, it can be found that the SNR of a complete linear frequency modulated (LFM) signal is equal to the SNR of the signal after intermittent transmission and reception processing. s 2 / (1-D s ), where D s This represents the duty cycle of the intermittently transmitted and received signals. Therefore, to compensate for this signal-to-noise ratio loss, the input power P after intermittent processing can be increased. si The original input signal power P i (1-D) s ) / D s 2 This can effectively compensate for the signal-to-noise ratio loss caused by intermittent processing.

[0013] The main beneficial effects of this invention include:

[0014] (1) By using the relationship between the signal-to-noise ratio of the complete signal after intermittent transmission and reception processing and the signal-to-noise ratio of the intermittently processed signal, the input signal power can be compensated, and the signal-to-noise ratio of the linear frequency modulated signal after intermittent transmission and reception in the microwave anechoic chamber can be obtained conveniently.

[0015] (2) It effectively solves the signal-to-noise ratio loss caused by intermittent transmission and reception processing, thereby realizing the equivalent simulation of the signal-to-noise ratio of linear frequency modulated signals in an anechoic chamber, and providing theoretical support for the equivalent simulation of radar power in radiation simulation. [Attached Image Description]

[0016] Figure 1 This is a flowchart of signal-to-noise ratio compensation for linear frequency modulated signals.

[0017] Figure 2 This sets the amplitude A of the linear frequency modulated signal to 1, and the time width T. p=100μs, bandwidth B =500MHz. Intermittent sampling period T s =0.8μs, sampling duty cycle D s =0.5, pulse width t s =0.4μs, the power P of the added Gaussian white noise n =10dBW, the output result of the original noisy linear frequency modulated signal and the signal after intermittent transmission and reception processing, after matched filtering.

[0018] Figure 3 This is the relationship between the ratio of the original average noise power to the average noise power after intermittent processing and the duty cycle after 100 Monte Carlo simulations.

[0019] Figure 4 It is the relationship between the ratio of the original signal output signal-to-noise ratio to the signal-to-noise ratio of the intermittently processed signal after 100 Monte Carlo simulations and the duty cycle.

[0020] Figure 5(a) shows the power P of the added Gaussian white noise. n =30dBW, and after energy compensation, the pulse pressure output simulation result is obtained.

[0021] Figure 5(b) shows the power P of adding different Gaussian white noise. n1 =10dBW, P n2 =20dBW, P n3 =35dBW. The impact of this compensation method.

[0022] Figure 5(c) shows the results after compensation for different input powers P after 100 Monte Carlo simulations. n The relationship between ∈[-20dBW,20dBW] and the output signal-to-noise ratio.

Detailed Implementation Methods

[0023] The invention will be further described below with reference to the accompanying drawings. The steps of the method for signal-to-noise ratio compensation after intermittent transmission and reception processing of a linear frequency modulated signal are as follows:

[0024] The first step is to calculate the peak power loss after intermittent transmission and reception of the linear frequency modulated signal.

[0025] Ideally, the waveform of an intermittent transmit / receive signal is a rectangular pulse train, which can be expressed as:

[0026]

[0027] Among them, T s For intermittent periods, t s The sub-pulse width is given by δ, * indicates convolution operation, δ(·) is the impulse function, and rect(·) is the rectangle function. The expression is:

[0028]

[0029] The frequency domain form of p(t) is:

[0030]

[0031] in Given the sampling frequency, sinc(x) = sin(πx) / (πx), D s =t s f s This indicates the duty cycle for intermittent signal transmission and reception.

[0032] The complex envelope of a carrier-de-carrier linear frequency modulated signal is represented as:

[0033]

[0034] Where A is the amplitude, T p Where is the pulse width, μ is the modulation slope, and the signal bandwidth is B = μT. p Its spectrum is

[0035]

[0036] The frequency response function of the matched filter for a linear frequency modulated signal is:

[0037] H(f) = KX * (f)exp(-j2πft0) ​​(6)

[0038] Letting t0 = 0, we can obtain the time-domain expression of the linear frequency modulated signal after the matched filter as follows:

[0039] y(t)=F -1 [X(f)H(f)]=KA 2 T p sinc(Bt) (7)

[0040] The peak power of the complete linear frequency modulated signal after passing through the matched filter is:

[0041] P = (KA) 2 T p ) 2 (8)

[0042] The time and frequency domains of the linear frequency modulated signal after intermittent transmission and reception processing are:

[0043]

[0044]

[0045] After intermittent transmission and reception processing, the linear frequency modulated signal enters the matched filter, and the output time domain is:

[0046]

[0047] In intermittent transmission and reception, the n=0th order pulse compression output is generally taken as the processing result. When n=0, the peak power of the signal after intermittent transmission and reception processing and passing through the matched filter is...

[0048] P s = (KA) 2 D s T p B) 2 (12)

[0049] Comparing equations (8) and (12), it can be seen that the difference between the peak power of the main lobe of the linear frequency modulated signal after intermittent transmission and reception and the original signal is the square of the duty cycle D. s 2 ,like Figure 2 As shown.

[0050] The second step is to calculate the average power loss after intermittent transmission and reception of noise.

[0051] Let P n (w) and The input noise n(t) and the output noise n are respectively. o The power spectral density of (t) is then

[0052]

[0053] The average power of the output noise is

[0054]

[0055] The power spectral density of white noise is

[0056]

[0057] Where N(f) is the frequency domain form of the input noise n(t), and T n Let be the duration of the noise signal. Its average output power after passing through the matched filter is...

[0058]

[0059] During intermittent transmission and reception, the channel switches back to the transmit channel after each signal reception to continue transmitting. Since noise is only received at the receive gate, intermittent transmission and reception processing is also required for the noise signal. For noise n(t), after intermittent transmission and reception processing, its processed form is:

[0060] n s (t)=n(t)(1-p(t)) (17)

[0061] The frequency domain of the noise signal after intermittent transmission and reception processing is:

[0062]

[0063] Intermittent transmission and reception processing will result in a noise signal duration T after processing. n Decrease, that is

[0064] T sn =(1-D s )T n (19)

[0065] Power spectral density is

[0066]

[0067] In intermittent transmission and reception, the n=0th order pulse compression output is generally taken as the processing result. Therefore, the average power E of the matched filter output of the noise signal after intermittent transmission and reception processing is... ns for

[0068]

[0069] Therefore, the average power output of the white noise signal after intermittent transmission and reception through matched filtering differs from the original signal by (1-D). s ),like Figure 3 As shown.

[0070] The third step is to compensate for the signal-to-noise ratio by modulating the transmitted signal energy.

[0071] The signal-to-noise ratio (SNR) of a matched filter output is the ratio of the peak power of the output signal to the average power of the noise. Therefore, the SNRs of the complete linear frequency modulated signal and the signal-to-noise ratio after intermittent transceiver processing are respectively...

[0072]

[0073]

[0074] Then the two are like Figure 4 As shown

[0075]

[0076] Therefore, to compensate for the loss in signal-to-noise ratio, the input signal power P after the interval can be increased. si The original input signal power P i (1-D) s ) / D s 2 times

[0077]

[0078] Figures 5(a), (b), and (c) verify the universality of the compensation method. Figure 5(a) shows the pulse pressure output results after adding different Gaussian white noise. It can be seen that the peak value of the compensated pulse pressure is similar to the peak value of the original signal. Figure 5(b) verifies that the compensation method is suitable for different Gaussian white noise. Figure 5(c) verifies that the compensation method is suitable for different input powers and can obtain a signal-to-noise ratio similar to the original signal.

Claims

1. A method for compensating the signal-to-noise ratio of intermittent transmission and reception of linear frequency modulated signals in a microwave anechoic chamber RF radiation simulation, characterized in that: The method includes the following steps: The first step is to calculate the peak power loss after intermittent transmission and reception of the linear frequency modulated signal. Intermittent signal transmission and reception For a pulse train with a rectangular envelope, a linear frequency modulated signal After intermittent transmission and reception, the pulse will be truncated into a series of sub-pulses. Both the intermittently processed signal and the complete signal are passed through a matched filter. After processing, the peak power loss after matched filtering was obtained by comparison. The second step is to calculate the average power loss after intermittent transmission and reception in the noise. Complete noise Noise after intermittent transmission and reception processing After being processed by matched filtering, the average output power of the two is obtained as follows: and The average power loss of the noise after intermittent transmission and reception is obtained by comparing the two. The third step is to perform signal-to-noise ratio compensation by modulating the transmitted signal energy. The signal-to-noise ratio (SNR) of a matched filter output is the ratio of the peak power of the output signal to the average power of the noise. A comparison reveals that the SNR of a complete linear frequency modulated (LFM) signal is higher than that of the signal after intermittent transmission and reception processing. ,in The duty cycle for intermittent transmission and reception; by increasing the input power after intermittent processing. Original input signal power of This compensates for the signal-to-noise ratio loss caused by intermittent processing.

2. The method for compensating the signal-to-noise ratio of intermittent transmission and reception of linear frequency modulated signals in microwave anechoic chamber radio frequency radiation simulation according to claim 1, characterized in that: The specific process of the first step is as follows: Ideally, the waveform of an intermittent transmit / receive signal is a rectangular pulse train, expressed as: (1) in, It is an intermittent period. " is the width of the sub-pulse, " indicates convolution operation, It is the impulse function. It is a rectangle function, and its expression is: (2) The corresponding frequency domain form is (3) in Sampling frequency, , Indicates the duty cycle of intermittent signal transmission and reception; The complex envelope of a carrier-de-carrier linear frequency modulated signal is represented as: (4) in, For amplitude, The pulse width. The modulation slope is and the signal bandwidth is . Its spectrum is (5) The frequency response function of the matched filter for a linear frequency modulated signal is: (6) make The time-domain expression of the linear frequency modulated signal after the matched filter is: (7) The peak power of the complete linear frequency modulated signal after passing through the matched filter is: (8) The time and frequency domains of the linear frequency modulated signal after intermittent transmission and reception processing are: (9) (10) After intermittent transmission and reception processing, the linear frequency modulated signal enters the matched filter, and the output time domain is: (11) when At that time, the peak power of the signal after intermittent transmission and reception processing and passing through the matched filter is (12)。 3. The method for compensating the signal-to-noise ratio of intermittent transmission and reception of linear frequency modulated signals in microwave anechoic chamber RF radiation simulation according to claim 1, characterized in that: The specific process of the second step is as follows: set up and Input noise and output noise The power spectral density, then (13) The average power of the output noise is (14) The power spectral density of white noise is (15) in Input noise The frequency domain form, The duration of the noise signal; Its average output power after passing through the matched filter is (16) For noise If intermittent transmission and reception processing is performed, the result after intermittent transmission and reception processing is: (17) The frequency domain of the noise signal after intermittent transmission and reception processing is: (18) Intermittent transmission and reception processing will result in a longer duration of noise signal after processing. Decrease, that is (19) Power spectral density is (20) During intermittent transmission and reception, take The pulse compression output is taken as the processing result. The average power of the matched filter output of the noise signal after intermittent transmission and reception processing is... for (21)。 4. The method for compensating the signal-to-noise ratio of intermittent transmission and reception of linear frequency modulated signals in microwave anechoic chamber RF radiation simulation according to claim 1, characterized in that: The specific process of the third step is as follows: The signal-to-noise ratio (SNR) of a matched filter output is the ratio of the peak power of the output signal to the average power of the noise. Therefore, the SNRs of the complete linear frequency modulated signal and the signal-to-noise ratio after intermittent transceiver processing are respectively... (22) (23) The ratio of the two is (24) Therefore, in order to compensate for the loss of signal-to-noise ratio, the input signal power after the interval is increased. Original input signal power of times (25)。

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